Hard disk drives are common information storage devices. Typically, referring to FIG. 1a, a disk drive unit 1′ contains a number of rotatable magnetic disks 15′ mounted on a spindle motor 17′, and a head stack assembly (HSA) 13′ which is rotatable about an actuator arm axis for accessing data tracks on the magnetic disks 15′ during seeking. The HSA 13′ includes at least one drive arm 131′ and HGA 132′. Typically, a spindling voice-coil motor (VCM) (not labeled) is provided for controlling the motion of the drive arm 131′.
Referring to FIGS. 1a and 1b, the HGA 132′ includes a floating magnetic head 12′ that can read data from magnetic media or write to selectively and a suspension 14′ to load or suspend the magnetic head 12′ thereon. When the hard disk drive is on, the spindle motor 17′ will rotate the disk 15′ at a high speed, and the magnetic head 12′ will fly above the disk 15′ due to the air pressure drawn by the rotated disk 15′. The magnetic head 12′ moves across the surface of the disk 15′ in the radius direction under the control of the VCM. With a different track, the magnetic head 12′ can read data from or write data to the disk 15′.
As shown in FIGS. 1b and 1c, the magnetic head 12′ includes a slider substrate 121′ having a trailing edge 122′ and a leading edge 123′, and a pole tip with a read/write element (not shown) embedded in the trailing edge. As illustrated in FIG. 1c, a plurality of bonding pads 124′ are arranged on the trailing edge 122′ and adapted for connecting to the electrical connection pads 144′ of the suspension 14′ by the way of solder joints 148′. Owing to the limitation of the size of the magnetic head 12′, the number of the bonding pads 124′ located on the trailing edge 122′ generally is six or eight, a pair of bonding pads 124′ are electrically connected to a read element for reading data from magnetic disk, a pair of bonding pads 124′ are electrically connected to a write element for writing data to magnetic disk, a pair of bonding pads 124′ are electrically connected to a thermal resistance for heating the pole tip, a pair of bonding pads 124′ are electrically connected to a sensor for adjusting the flying height of the magnetic head 12′ by means of inducting the interaction between the magnetic head 12′ and the magnetic disk 15′. With increased demand of data storage for capacity of disk drive unit 1′, the capacity of disk drive unit 1′ has always been the focus of research. But in recent years, higher request for the reliability of the magnetic head 12′ has also been put forward. The magnetic head 12′ as the core of the disk drive unit 1′ is used to read and write data message, the capacity of disk drive unit 1′ is determined by flying height and lubricating property of magnetic head 12′, and surface condition of magnetic head 12′ and magnetic disk 15′, while the reliability of the bonding pads 124′ markedly affect the reliability of the magnetic head, and further affect the reliability of the disk drive unit.
As shown in FIG. 1c-1f, the slider substrate 121′ further includes an over coat layer 1262′ having the trailing edge 122′ on which the bonding pads 124′ formed. Several copper columns 1242′ are buried in an over coat layer 1262′ for connecting with read/write element in the slider substrate 121′ and connecting with the bonding pads 124′. Each bonding pad 124′ contains a titanium or tantalum layer 1244′ formed on the trailing edge 122′ and connected to the copper column 1242′, a ferro-nickel layer 1246′ formed on the titanium or tantalum layer 1244′ and a gold layer 1248′ formed on the ferro-nickel layer 1246′ for soldering. Due to small distance between two adjacent bonding pads, the adjacent bonding pads are prone to shorting-circuit during soldering process, thus damage the magnetic head. In order to meet the needs of the test, the dimension of the bonding pads should match the size of the tester probe, and because of small magnetic head dimension, it's difficult for the magnetic head to carry more bonding pads with additional function at its trailing edge, thereby limiting the function and performance of the magnetic head.
Hence, it is desired to provide a magnetic head, an HGA, and a disk drive unit to overcome the above-mentioned drawbacks.